This invention relates generally to folding knives, and, more broadly, to the folding instruments, the working part of which can be locked in an open position.
Folding knives and folding instruments used for various purposes are known from the prior art. Many such tools and knives include a blade locking mechanism, securing the blades in the working, i.e., the open, position. An example of such mechanism is shown in U.S. Pat. No. 6,941,661.
Some (but not all) of the known lock mechanism designs are symmetrical about a plane parallel to the sides of the tang of the blade, lying equidistantly between the sides. Examples of such designs include “lock back,” “mid lock,” “axis lock,” “arc lock” etc. This symmetry allows for an equally convenient use of the folding knife or instrument for both right- and left-handed users. Such convenience can be considered an advantage as compared with asymmetrical designs of locking mechanisms (liner lock, frame/integral lock, button lock, compression lock, etc.) which limit usability for left-handed users (or for right-handed users if the lock is specifically designed for left-handed users). Another advantage of a symmetrical design is the ease of design and manufacturing of the resulting folding knife or instrument because, in the case of symmetry, many parts can be standardized unlike for knives and tools having locks with an asymmetrical structure.
Some of the famous locks of symmetrical designs allow its user to unlock and fold the blade or tool from the open (i.e., operating) position using the same hand in which the user holds the knife/tool. Thus, such locks (referred to as one-armed symmetrical locks) have the advantage of ease of use compared to the locks which require the use of two hands (lock back, for example).
Some of these locks include fairly compact designs which allow a manufacturer to make a folding knife or a tool of smaller dimensions, which, in turn, can also be considered a competitive advantage.
In addition, benefits of the above-described designs include safety of use, ease of manufacturing technology, and an ability to make a lighter folding knife or tool.
Keeping in mind strength and reliability of construction, following is the list of important parameters advantageous for construction of a locking mechanism for a folding knife/instrument from the point of view of convenience of use:                Symmetry with respect to the plane of the blade or tool        The ability to use the folding knife with one hand without the aid of the second hand        Adaptability to design and production, the possibility of unification of parts        Compactness        Use safety, specifically, the ability to unlock the lock without the need of placing fingers in a blade rotation area (as it has to be done in liner locks or lock back locks, for example).        The ability to reduce the weight of a folding knife/instrument.        
The invention described and claimed herein is superior to the described prior art locks. First, in contrast to the prior art locks, presently described and claimed locking mechanism does not need to include handle-held lining plates of solid steel or titanium alloys. For example, in axis locks the load on the folding blade or tool is transferred from the blade/tool tang through the locking pin onto the metal liners. In arc locks, this load is transferred by a swing arm but also onto the metal liners. In ball bearing locks, a metal ball passes the load onto an additional element secured between the metal liners. Compared to all of these prior art design, in the presently disclosed and claimed locking mechanism, the load of folding the blade/tool is transferred by the tang onto a stop pin through an element rotating about the same pin. Thus, the entire load directed to the blade/tool in the unfolding or folding direction, is assumed by the stop pin secured at the front of the handle, that restricts the movement of the folding blade and, at the same time, functions as a rotational axis for the main locking element.
A similar load transfer scheme in the stopper (resistant) pin is described in the patent Tri-Ad Lock by Andrew Demko. However, the entire locking mechanism of the above-mentioned patent is quite different the presently disclosed locking mechanism. Tri-Ad lock design is nearly identical to a previously known lock back mechanism, or its later modification, known as the Mid lock. Tri-Ad Lock design is not compact and takes up a lot of space in the blade folding plane, that makes folding knives with Tri-Ad Lock relatively non-compact themselves when folded. Further, it is very uncomfortable to fold a knife with a Tri-Ad lock with one hand and, during such process of folding, it is practically necessary to place some fingers of the same hand into the blade turning plane, thereby increasing the danger of injury.
The design of the present invention does not require metal plate liners. Stop pin can be installed directly into the base of the handle, which may be made of durable and lightweight material (e.g. aluminum alloys, textolite, cast plastics, etc.). Elimination of metal plate liners, as well as, the size reduction of the lock elements enables the manufacturers to make the folding knife lighter and more compact than in the case of other known symmetric lock designs.
Finally, the presently described and claimed locking mechanism is arranged in such a way that sliding elements, protruding from the handle and secured on the main locking element, allow a user to hold the open knife/tool with one hand and to use the fingers of the same hand to move the locking mechanism (releasing the blade from its locked position) by pressing on one of sliders and to fold the blade/tool. The direction in which the user needs to act on the slider protruding from the handle is very natural and does not force the user to make awkward manipulations with an open knife in his/her hand. In no time, during the above blade releasing and closing process, do user's fingers need to be placed in the dangerous zone of blade rotation making manipulations of the folding knife safer.